The invention relates to a bar holder arrangement for holding bar stock material in a manner to permit feed of the bar stock material to a machine tool.
The invention is particularly applicable to a bar holder arrangement of the kind disclosed in the specification of our U.S. Pat. No. 3,802,689.
This Patent specification discloses a bar holder arrangement for holding bar stock material to be fed to a machine tool. The arrangement comprises a frame and at least one elongated bar holder mounted in the frame. The bar holder comprises a plurality of levers each pivotably mounted on an elongated member of the bar holder. Each of the levers has at one of its ends an upstanding member having a semicircular recess therein and at the other of its ends a further upstanding member having a semicircular recess therein. The levers are disposed along the elongated member that said upstanding member of one lever co-operates with said further upstanding member of the next adjacent lever to define a circular receiving means for a length of bar stock material. Pivoting means for said levers is effective to separate the upstanding member of each lever from the further upstanding member of an adjacent one of the levers to open the bar holder and enable a length of bar stock material to be moved to a position in which it is received by said circular receiving means when the levers are moved to respective positions in which the upstanding member of each of the levers abuts the further upstanding member of an adjacent one of the levers to form said circular receiving means.
The aforesaid Patent specification further discloses that the semicircular recesses in the upstanding member and further upstanding member are provided by inserts received in said members and said further members.
In practice the inserts are changed when a change is made in the diameter of the bar stock material being machined and held in the bar holder arrangement so that the circular receiving means defined by the bar holder arrangement are each a clearance fit around the bar stock material.
Where feed means, to feed bar stock material held in the bar holder arrangement longitudinally of the bar holder arrangement, is of the kind comprising a slug, the front end of which abuts the rear end of the bar stock material rather than of the kind where the bar stock material is fed by feed means which act on a portion of the bar stock material projecting from the front end of the bar holder arrangement, difficulties arise in that the slug is normally of similar diameter to the maximum size of bar stock material which can be held in the bar holder, for example 13/4 inches diameter. Thus, the slug cannot be passed through the circular receiving means when such circular receiving means are set to hold bar stock material of smaller diameter, for example 1/4 inch diameter.